Connect the Portainer Server to an existing Portainer Agent

With Portainer we can monitor multiple Docker Swarms from one Portainer Server. To connect an existing Portainer server to an agent

Configure the Agent

• For security reasons, by default, the Portainer Agent only accepts connection from the first Portainer Server it encounters. To enable the Portainer Agent to connect to multiple Portainer Servers, add the AGENT_SECRET environment variable to the docker-compose.yml file of the Agent. This is necessary if you launch a Portainer Server on the Docker host and connect to the local Agent to test it. Without specifying the AGENT_SECRET, another Portainer Server cannot connect to the same agent.
• Publish the Agent port on the host network

    environment:
      # REQUIRED: Should be equal to the service name prefixed by "tasks." when
      # deployed inside an overlay network
      AGENT_CLUSTER_ADDR: tasks.agent
      # AGENT_PORT: 9001
      # LOG_LEVEL: debug
      AGENT_SECRET: my_secret_token
    ports:
      - target: 9001
        published: 9001
        protocol: tcp
        mode: host

Configure the Server

• Add the AGENT_SECRET environment variable to the docker-compose.yml file of the Server

    environment:
      AGENT_SECRET: my_secret_token

Add the endpoint to the Portainer Server

• Log into the Portainer Server
• Navigate to the Endpoints page
• Click the Add Endpoint button
• Select the Agent endpoint type
• Enter the IP address and the port number ( by default 9001 ) of the Portainer Agent